When could I take a haircut due to sheloshes yemei hagbola. Does it start wed night or thu morning?
For those who are stringent to refrain from haircuts until the days of hagbalah (meaning, those who keep the “second half” of the Omer), one should not take a haircut until the morning of the first day of hagbalah.
Those who refrain from taking a haircut during the entire Omer period (al pi kabbalah), should only take a haircut on Erev Shavuos, or Friday of this year.
Sources: Mishnah Berurah 493:15.